After Margot Kidder expressed her disgust about the firing of Richard Donner to producers Alexander Salkind and Ilya Salkind, her role was cut to 12 lines and less than five minutes of screen time. In the film's 2006 DVD commentary, Ilya Salkind says there was little need for Lois Lane in this movie because her relationship with Superman ended at the end of Superman II (1980).
Christopher Reeve was not happy with the film, and often expressed in interviews that he hated how it turned out. He initially swore never to play the role again. He was persuaded to make Superman IV: The Quest for Peace (1987) in exchange for more input on the script.
This is the first time Christopher Reeve had top billing in a Superman movie. In Superman (1978) he was behind Marlon Brando and Gene Hackman. In Superman II (1980) he was behind Hackman.
When it was first revealed to producers that Lana Lang would be a single mother, a comic book was quickly written explaining how Lana came to be in that situation.
Christopher Reeve threatened not to return for this film, to protest Richard Donner's firing and because he hated the script. With the film already in pre-production, the producers scrambled to find an actor to play Superman. John Travolta was approached, but declined. Jeff Bridges and Kurt Russell were also considered, but they weren't interested. A few days before filming was set to begin, the Salkinds settled on Tony Danza as Clark Kent/Superman. Richard Lester was mortified with the casting of Danza, and pleaded for Reeve to return. Reeve eventually agreed, if he was allowed to change the script. The producers agreed. That's one popular rumor. Another is once Reeve found out Danza was lined up to replace him; he quickly got intimidated; having assumed the movie would be cancelled without his participation; and at that point Reeve relented.
Aaron Smolinski: (at around 6 mins) Aaron Smolinski who played baby Clark Kent in Superman (1978) appears uncredited as a little boy waiting outside a photo booth while Clark Kent is changing into Superman.
Paul Weston: (at around 5 mins) accidentally breaks off the door handle in an attempt to rescue the drowning driver from the car. The stunt coordinator was Terence Stamp's double in Superman II (1980).